Pump device with outer housing and flow path

Abstract

Pump device (1) comprising: a piezoelectric pump (10) comprising a pump housing having an inlet (400) and an outlet (520), a vibrating plate (31) arranged inside the pump housing and dividing a space (500) inside the pump housing into a first space (501) on one side near the inlet (400) and a second space (502) on one side near the outlet (520), and a piezoelectric element (20) arranged on the vibrating plate (31);and an outer casing (70) forming a flow path enabling communication between an outer inlet (701), which communicates with the outside, and the inlet (400), characterized in that a first main surface of the outer casing is opposite an outer main surface (40op) of the pump casing in which the inlet (400) is formed, and the flow path is located at least between the outer main surface (40op) of the pump casing and the first main surface of the outer casing (70), wherein the flow path is provided between an outer surface that differs from the outer main surface (40op) of the pump casing in which the inlet (400) is formed and a surface that differs from the opposite first main surface of the outer casing.

Description

The present invention relates to a pump device including a piezoelectric pump that transports a fluid by causing a vibration plate to vibrate using a piezoelectric element.Patent Document 1 discloses a pump using a piezoelectric element. The pump includes a pump housing and a vibration plate. The pump housing has a pump chamber therein. The vibration plate is disposed in the pump chamber. Here, the vibration plate is supported by the pump housing to be capable of vibrating.The vibration plate divides the pump chamber into a first pump chamber and a second pump chamber. The first pump chamber communicates with the space outside the pump housing via an inlet formed in the pump housing. The second pump chamber communicates with the space outside the pump housing via an outlet formed in the pump housing.The pump draws a fluid such as air from outside the pump housing into the inside of the pump chamber via the inlet, and discharges the fluid inside the pump chamber from the pump housing via the outlet by using vibrations of the vibration plate.List of ReferencesPatent DocumentPatent Document 1: International Publication No. WO 2016 / 175 185 A1However, the pump disclosed in Patent Document 1 generates heat due to vibration of the vibration plate. In addition, a problem may arise in the operation of the pump when the temperature of the pump including the vibration plate becomes high.EP 2 557 312 A1 discloses a pump device which comprises a piezoelectric pump having a pump housing having an inlet and outlet. The housing also defines a flow path that allows communication between an external inlet and the inlet.Therefore, an object of the present invention is to provide a pump device having high heat dissipation capability.Solution of the ProblemA pump device of the present invention includes a piezoelectric pump and an outer housing. The piezoelectric pump includes a pump housing having an inlet and an outlet, a vibration plate disposed inside the pump housing and partitioning a space inside the pump housing into a first space on a side near the inlet and a second space on a side near the outlet, and a piezoelectric element disposed on the vibration plate. The outer housing forms a flow path that allows communication between an outer inlet, which is connected to the exterior, and the inlet. A first major surface of the outer housing faces an outer major surface of the pump housing in which the inlet is formed. The flow path is at least between the outer main surface of the pump housing and the first main surface of the outer housing.With this configuration, heat generated by the piezoelectric pump and transferred to an outer main surface of a wall of the pump housing in which the inlet is formed is cooled by a fluid flowing along the flow path. Since the fluid is at a low temperature before being sucked into the piezoelectric pump and the area of the outer main surface of the wall in which the inlet is formed is large, the cooling effect with respect to the heat of the piezoelectric pump is high.According to the present invention, the heat dissipation capability of a pump can be improved.Brief Description of the Drawings:[FIG. 1 ] FIG. 1(A) is a plan view of a pump device according to a first embodiment, FIG. 1(B) is a side-plane sectional view showing the configuration of the pump device according to the first embodiment, and FIG. 1(C) is a side view of the pump device according to the first embodiment.[FIG. 2 ] FIG. 2 is an exploded perspective view of the pump device according to the first embodiment.[FIG. 3] FIG. 3 is a diagram illustrating the approximate flow of a fluid generated by the pump device according to the first embodiment.[FIG. 4] FIG. 4 is a graph illustrating changes over time at an inlet surface temperature for configurations of the present application and a comparative example.[FIG. 5 ] FIG. 5(A) is a graph illustrating the relationship between the temperature of the piezoelectric pump and the fluid transport efficiency, and FIG. 5(B) is a graph illustrating the relationship between the elapsed time and the suction pressure.[FIG. 6 ] FIG. 6(A), FIG. 6(B), and FIG. 6(C) are side-plane sectional views each illustrating a first modification, a second modification, and a third modification of the pump device according to the first embodiment.[FIG. 7 ] FIG. 7 is a five-view diagram illustrating the configuration of a fourth modification of the pump device according to the first embodiment.[FIG. 8] FIG. 8 is a side-plane sectional view illustrating the configuration of a pump device according to a second embodiment.[FIG. 9 ] FIG. 9 (A) is a graph illustrating changes with time at a discharge temperature for configurations of the present application and a comparative example, and FIG. 9 (B) is a graph illustrating the relationship between the elapsed time and the suction pressure.[FIG. 10 ] FIG. 10 (A) is a side plane sectional view illustrating the configuration of a pump device according to a third embodiment, and FIG. 10 (B) is a side plane sectional view illustrating an example of the wiring for the pump device according to the third embodiment.[FIG. 11 ] FIG. 11 is a graph illustrating changes with time at a discharge temperature for configurations of the present application and a comparative example.[FIG. 12] FIG. 12 is a side-plane sectional view illustrating the configuration of a pump device according to a fourth embodiment.[FIG. 13 ] FIGS. 13(A) and 13(B) are sectional plan views illustrating the configurations of outer housings of pump devices according to a fifth embodiment.[FIG. 14] FIG. 14 is a graph illustrating changes with time at a discharge temperature for configurations of the present application and a comparative example.DESCRIPTION OF THE EMBODIMENTS(First Embodiment)A pump device according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1(A) is a plan view of the pump device according to the first embodiment. FIG. 1(B) is a side-plane sectional view illustrating the configuration of the pump device according to the first embodiment. FIG. 1(C) is a side view of the pump device according to the first embodiment. FIG. 1(B) is a diagram illustrating a side plane in a direction perpendicular to an opening plane of an outer inlet, and FIG. 1(C) is a side view in which the opening plane of the outer inlet is seen from the front. FIG. 2 is an exploded perspective view of the pump device according to the first embodiment. FIG. 3 is a diagram illustrating the approximate flow of a fluid generated by the pump device according to the first embodiment.In each of the drawings illustrated in the following embodiments, the shapes (dimensions) of the individual constituent elements are partially or fully enlarged to make the description more comprehensible.As illustrated in FIGS. 1(A), 1(B), 1(C), 2 and 3, a pump device 1 includes a piezoelectric pump 10 and an outer housing 70. The outer housing 70 and the piezoelectric pump 10 contact each other at the sides thereof in the vicinity of the inlets 400 of the piezoelectric pump 10.Configuration of Piezoelectric Pump 10)The piezoelectric pump 10 includes a piezoelectric element 20, a flat plate member 300 including a vibration plate 31, a first housing member 40, a second housing member 50, and a third housing member 60.The piezoelectric element 20 is composed of a piezoelectric disc and driving electrodes. The driving electrodes are formed on both main surfaces of the piezoelectric disc.The flat plate member 300 includes the vibration plate 31, a bottom part 32, and a support part 33. The flat plate member 300 is, for example, a flat plate formed of a metal or the like. The shape of the flat plate member 300 in a plan view is a rectangular shape. The surfaces as viewed in a plan view are the main surfaces of the flat plate member 300. The flat plate member 300 is realized using a single flat plate, for example. In other words, the vibration plate 31, the bottom part 32, and the support part 33 are integrally formed as a single flat plate. The vibration plate 31 is a disk. The bottom portion 32 is formed so as to surround the outer periphery of the vibration plate 31. The support part 33 connects the vibration plate 31 and the bottom part 32 to each other. Here, the support part 33 connects the vibration plate 31 and the bottom part 32 to each other in a localized manner at multiple locations along the outer periphery of the vibration plate 31. With this configuration, the vibration plate 31 is supported so as to be capable of vibrating with respect to the bottom part 32.The first housing member 40 is, for example, a flat plate formed of a metal or the like. The material of the first housing member 40 preferably has a prescribed rigidity and thermal conductivity. The first housing member 40 has a substantially rectangular shape in plan view. The surfaces, as viewed in a plan view, are the major surfaces of the first housing member 40. the first housing member 40 has a plurality of inlets 400. When the piezoelectric pump 10 is viewed in a plan view, the plurality of inlets 400 overlap the vibration plate 31, for example. the plurality of inlets 400 are through holes penetrating between the main surfaces of the first housing member 40. The plurality of inlets 400 have, for example, a circular shape in a cross section parallel to the main surfaces of the first housing member 40. The diameter of this circular shape is, for example, 0.8 mm.The second case member 50 has a main plate 51 and a side wall 52, and is shaped like a box. The second housing member 50 is formed of, for example, a metal or the like. The main plate 51 and the side wall 52 are flat plates. More specifically, the shape of the main plate 51 in a plan view is a rectangular shape, and the main plate 51 has substantially the same area and shape as the first case member 40. The side wall 52 extends in a direction perpendicular to the main surfaces of the main plate 51. the side wall 52 is disposed along an outer peripheral edge of the main plate 51. Thus, the second housing member 50 is formed in a box-like shape. A nozzle 510 is formed on the main plate 51. The nozzle 510 has a cylindrical shape. The nozzle 510 is connected to a main surface of the main plate 51 located on the opposite side from the main surface of the main plate 51 located near the side wall 52.The second housing member 50 has an outlet 520. The outlet 520 is a through hole penetrating through the nozzle 510 and the main plate 51. When the piezoelectric pump 10 is viewed in a plan view, the outlet 520 overlaps the vibration plate 31, for example.The third housing member 60 is a frame having a prescribed thickness. The outer shape of the third housing member 60 is substantially the same as the outer shape of the first housing member 40.The third housing member 60 is connected to a main surface of the first housing member 40. The bottom portion 32 of the flat plate member 300 is connected to the third housing member 60. The side wall 52 of the second housing member 50 is connected to the bottom portion 32 of the flat plate member 300. With this configuration, a pump housing having an inner space 500 therein is realized. The inner space 500 communicates with the space outside the pump housing on the side near the first housing member 40 via the inlets 400. The inner space 500 communicates with the space outside the pump housing on the side near the second housing member 50 via the outlet 520. As illustrated in FIG. 3, the inner space 500 is divided into a first space 501 and a second space 502 by the vibration plate 31. The first space 501 is a space on the vibration plate 31 side in the vicinity of the inlets 400, and the second space 502 is the space on the vibration plate 31 side in the vicinity of the outlet 520. The first space 501 and the second space 502 communicate with each other via through holes provided in the support part 33, and penetrate through the flat plate member 300.The piezoelectric element 20 is disposed on a main surface of the vibration plate 31 in the second space 502.With this configuration, the piezoelectric pump 10 transports a fluid as described next. The principles of fluid transport are known from the prior applications of the assignee of the present application and so forth and, therefore, a simplified description will be given.The piezoelectric element 20 is connected to a control unit, which is not illustrated. The control unit generates an AC voltage and applies the AC voltage to the piezoelectric element 20. Consequently, the piezoelectric element 20 expands and contracts, and the vibration plate 31 undergoes bending vibration. Thus, the volumes of the first space 501 and the second space 502 change, and a fluid is sucked into the inside of the piezoelectric pump 10 from the inlets 400 and discharged to the outside from the outlet 520 due to these changes, as illustrated in FIG. 3.With this configuration, the piezoelectric pump 10 generates heat due to the vibration of the vibration plate 31. The pump device 1 of the invention of the present application is capable of dissipating heat from the piezoelectric pump 10 due to being provided with the outer housing 70 to be described next.(Configuration of Outer Housing 70)As illustrated in FIGS. 1(A), 1(B), 1(C), 2, and 3, the outer housing 70 includes a main flat plate 71, a main flat plate 73, a side wall 721, a side wall 722, and a side wall 723. The main flat plate 71 and the main flat plate 73 are formed of a material having high thermal conductivity. It is sufficient that at least the main flat plate 73 is formed of a material having high thermal conductivity, but it is preferable that the main flat plate 71 is also formed of a material having high thermal conductivity. The main flat plate 71 and the main flat plate 73 are arranged such that the main surfaces thereof are opposed to each other and are substantially parallel to each other. The surface of the main flat plate 71 that faces the main flat plate 73 corresponds to "a first main surface of an outer case" of the present invention. Three sides of the outer periphery of the main flat plate 71 and three sides of the outer periphery of the main flat plate 73 are connected to each other by the side wall 721, the side wall 722, and the side wall 723. With this configuration, the outer housing 70 has a box-like shape having an inner space 700.The outer housing 70 has an outer inlet 701. The outer inlet 701 is realized by a region in which the main flat plate 71 and the main flat plate 73 are not connected to each other by the side wall 721, the side wall 722, or the side wall 723. In other words, in this embodiment, the outer inlet 701 is realized due to the outer housing 70 not being provided with a side wall of the box-like shape. The opening plane of the outer inlet 701 has, for example, a rectangular shape as illustrated in FIG. 1(C).The outer housing 70 has a plurality of outlet openings 730. The plurality of outlet ports 730 are through-holes penetrating between the main surfaces of the main flat plate 73. The plurality of discharge ports 730 have, for example, a circular shape in a cross section parallel to the main surfaces of the main flat plate 73. The size of the outlet ports 730 in a plan view (as viewed in a direction perpendicular to the opening planes) is preferably larger than or equal to the size of the inlets 400. The plurality of discharge ports 730 are arranged in the same pattern as the inlets 400 of the piezoelectric pump 10 described above. The inner space 700 communicates with the space outside the outer housing 70 on the side near the main flat plate 73 via the plurality of outlet ports 730.(Installation configuration of Piezoelectric Pump 10 and Outer Housing 70 and Operation Effect of Pump Device 1)The main flat plate 73 of the outer housing 70 contacts an outer main surface 40 opof the first housing member 40 of the piezoelectric pump 10. the outer main surface 40 opof the first housing member 40 is a surface of the first housing member 40 located on the opposite side from the main surface of the first housing member 40 that is opposed to the first space 501, and is a surface that forms an outer surface of the piezoelectric pump 10.At this time, the outer housing 70 and the piezoelectric pump 10 are arranged such that the outlet ports 730 of the outer housing 70 and the inlets 400 of the first housing member 40 overlap (communicate with each other).As described above, in this configuration, when the piezoelectric pump 10 draws in a fluid from the inlets 400, the fluid is supplied to the inlets 400 via the outer inlet 701, the inner space 700, and the outlet ports 730 of the outer housing 70. In other words, the fluid is transported from the outside of the outer housing 70 into the inside of the inner space 700 of the outer housing 70 via the outer inlet 701. The fluid is transported through the interior of the internal space 700 to the outlet ports 730, and the fluid then flows into the inlets 400 from the outlet ports 730. In other words, the inner space 700 is a fluid "transport path" according to the present invention.With the above-described configuration, in the pump device 1, the fluid transport path in the outer housing 70 is parallel to the outer main surface 40 opof the first housing member 40. At this time, the transport route is opposed to substantially the entire outer main surface 40 opof the first case member 40. Therefore, heat can be dissipated over a wide range. Therefore, the heat dissipation effect for the piezoelectric pump 10 through the outer housing 70 is improved.In addition, since the fluid flows along the transport path before being sucked into the piezoelectric pump 10, the fluid flowing along the transport path is at a lower temperature than the fluid inside the piezoelectric pump 10 and the fluid discharged to the outside from the outlet 520. Therefore, heat is more effectively dissipated from the first housing member 40, i.e., the piezoelectric pump 10, due to the configuration of the pump device 1 that is used.Further, a height D 700 of the inner space 700 is preferably small. This makes it possible to increase the speed of the fluid transported along the transport route (inner space 700). Consequently, heat is more effectively dissipated from the first housing member 40, i.e., the piezoelectric pump 10. The lower limit of the height D 700 is preferably set such that the maximum amount of fluid transported in the inner space 700 is greater than or equal to the maximum amount of fluid that can be drawn in through the inlets 400 determined by the performance of the piezoelectric pump 10. This prevents the shape of the internal space 700 from becoming a rate-limiting factor for the performance of the piezoelectric pump 10. Therefore, heat is effectively dissipated from the piezoelectric pump 10 without reducing the performance of the piezoelectric pump 10.Further, a height D 701 of the outer inlet 701 is preferably greater than or equal to the height D 700 of the inner space 700. Thus, the amount of the fluid supplied to the inner space 700 is not limited by the outer inlet 701. Therefore, the shape of the outer inlet 701 can be prevented from becoming a rate-limiting factor for the fluid transported in the inner space 700. Although a comparison of the height D 701 of the outer inlet 701 and the height D 700 of the inner space 700 is illustrated here, the shape of the outer inlet 701 may be specified using, for example, an area in a direction perpendicular to the direction in which the fluid is transported.FIG. 4 is a graph illustrating changes over time at an inlet surface temperature for configurations of the present application and a comparative example. In FIG. 4, the horizontal axis represents the elapsed time from the start of driving the piezoelectric pump 10, the vertical axis represents the inlet surface temperature of the piezoelectric pump 10, that is, the temperature of the outer main surface 40 opof the first housing member 40. The comparative example illustrates a configuration that does not have a heat dissipation structure like that of the invention of the present application.As illustrated in FIG. 4, the temperature of the inlet surface increases with the lapse of time in both the configurations of the present application and the comparative configuration. However, the rate of increase in temperature may be decreased, and the temperature achieved may be decreased by using the configurations of the present application. For example, an upper limit temperature Tth at which driving is stopped to prevent erroneous operation is set for the piezoelectric pump 10. This upper limit temperature Tth is reached in the comparative example, while the upper limit temperature is not reached in the configurations of the present application. Therefore, the piezoelectric pump 10 can be stably driven for a longer time as compared with the comparative example of the related art.In FIG. 4, the features of the pump device 1 according to the first embodiment and a pump device 1C (see FIG. 8 ) according to a second embodiment described later are illustrated. Basically, the pump device 1C according to the second embodiment has a configuration in which a side surface of the piezoelectric pump 10 is caused to also contact an outer housing 70C. In the piezoelectric pump 10, the area of the outer main surface 40 opis large, and the area of the side surface is smaller than that of the outer main surface 40 op. When the piezoelectric pump 10 is structured such that the vibration plate 31 and the first housing member 40 are close to each other and the vibration plate 31 and the first housing member 40 move closer to each other due to the vibration, the heat of the vibration plate 31 is mainly transferred to the first housing member 40. In this case, as illustrated in FIG. 4, the heat dissipation effect of the first housing member 40 for the same flow rate is improved by using the configuration of the pump device 1 according to the first embodiment, as compared with using the configuration of the pump device 1C according to the second embodiment. In other words, the heat dissipation effect of the inlet surface for a given flow rate is improved by using the configuration of the pump device 1.FIG. 5(A) is a graph illustrating the relationship between the temperature of a piezoelectric pump and the fluid transport efficiency. FIG. 5(B) is a graph illustrating the relationship between the elapsed time and the intake pressure. The "suction pressure" refers to the pressure of a suction device that performs suction using a piezoelectric pump.As illustrated in FIG. 5(A), the transport efficiency of the piezoelectric pump decreases as the temperature increases. Therefore, as illustrated in FIG. 5(B), the start time of decreasing the suction pressure can be delayed as compared with the comparative example by using the configuration of the piezoelectric pump 10. In other words, a suction device using the piezoelectric pump 10 is capable of maintaining a prescribed suction pressure for a longer time than a suction device using the comparative example.

[0042] (Modifications of Configuration of Pump Device According to First Embodiment)FIG. 6(A) is a side-plane sectional view illustrating the configuration of a first modification of the pump device according to the first embodiment, FIG. 6(B) is a side-plane sectional view illustrating the configuration of a second configuration of the pump device according to the first embodiment, and FIG. 6(C) is a side-plane sectional view illustrating the configuration of a third modification of the pump device according to the first embodiment. FIG. 7 is a five-view diagram illustrating the configuration of a fourth modification of the pump device according to the first embodiment.A pump device 1A 1 illustrated in FIG. 6(A) is different from the pump device 1 described above in the configuration of an outer housing 70A 1. The remaining configuration of the pump device 1A 1 is the same as that of the pump device 1, and a description of identical parts will be omitted.The outer housing 70A 1 differs from the outer housing 70 in that the outer housing 70A 1 has an outer inlet 702. The outer inlet 702 is disposed at a different position from the outer inlet 701 in the outer housing 70A 1. With this configuration, the outer housing 70A 1 has a plurality of outer inlets.With this configuration, the pump device 1A 1 also performs the same heat dissipation effect as the pump device 1 described above. In addition, because the outer housing 70A 1 has multiple outer inlets, it is capable of more reliably preventing the outer inlets from being a rate limiting factor for fluid transport.A pump device 1A 2 illustrated in FIG. 6(B) is different from the pump device 1 described above in the configuration of an outer housing 70A 2. The remaining configuration of the pump device 1A 2 is the same as that of the pump device 1, and a description of identical parts will be omitted.The outer case 70A 2 has an opening in the main flat plate 73 at a position overlapping the first case member 40 of the piezoelectric pump 10. The first case member 40 closes the opening of the main flat plate 73. in other words, the first case member 40 is exposed on the inner space 700 side of the outer case 70A 2, and forms a part of a wall that forms the inner space 700 of the outer case 70A 2.Thus, a fluid flowing through the inner space 700, i.e., the flow path, directly contacts the outer main surface 40 opof the first housing member 40.A pump device 1A 3 illustrated in FIG. 6(C) is different from the pump device 1 described above in the configuration of an outer housing 70A 3. The remaining configuration of the pump device 1A 3 is the same as that of the pump device 1, and a description of identical parts will be omitted.The outer case 70A 3 has an opening in the main flat plate 73 at a position overlapping the first case member 40 of the piezoelectric pump 10. The area of the opening is smaller than the area of the outer main surface 40 opof the first case member 40. with this configuration, the outer main surface 40 opof the first case member 40 contacts the main flat plate 73 and the side wall 723 along a part of the outer peripheral edge. In this case, a part of the first housing member 40 is exposed on the inner space 700 side of the outer housing 70A 3 and forms a part of a wall that forms the inner space 700 of the outer housing 70A 3.Thus, a fluid flowing through the inner space 700, i.e., the flow path, directly contacts the outer main surface 40 opof the first housing member 40. In addition, in this case, the outer main surface 40 opof the first housing member 40 contacts the outer housing 70A 3 along a part of the outer circumferential edge. This makes it easier to fix the first housing member 40 to the outer housing 70A 3.A pump device 1B illustrated in FIG. 7 is different from the pump device 1 described above in the configuration of an outer housing 70B. The remaining configuration of the pump device 1B is the same as that of the pump device 1, and a description of identical parts will be omitted.The outer housing 70B includes a flat main plate 710 and a plurality of cylindrical members 790. The main flat plate 710 is disposed so as to be spaced apart from and parallel to the outer main surface 40 opof the first case member 40 of the piezoelectric pump 10. The main flat plate 710 and the first housing member 40 are connected to each other by the plurality of cylindrical members 790.In this configuration, a space 700B between the first housing member 40 and the main flat plate 710 forms a flow path. The part of the space 700B flush with the side surface of the piezoelectric pump 10 forms an outer inlet 701B. With this configuration, the pump device 1B also performs the same heat dissipation effect as the pump device 1 described above. Further, in this configuration, the outer main surface 40 opof the first housing member 40 of the piezoelectric pump 10 forms a wall surface of the flow path. Therefore, the heat dissipation effect is improved. In addition, with this configuration, the configuration of the outer housing 70B can be simplified. In this configuration, the main flat plate 710 may be realized by an outer wall of a device in which the piezoelectric pump 10 is installed. Therefore, the above-described heat dissipation effect can be obtained by simply installing the piezoelectric pump 10 in the device.(Second Embodiment)A pump device according to a second embodiment will be described with reference to the drawings. FIG. 8 is a side-plane sectional view illustrating the configuration of the pump device according to the second embodiment.As illustrated in FIG. 8, the pump device 1C according to the second embodiment is different from the pump device 1 according to the first embodiment in the configuration of an outer housing 70C. The remaining configuration of the pump device 1C is the same as that of the pump device 1, and a description of identical parts will be omitted.The outer housing 70C is different from the outer housing 70 in the shape of a main plate on the side near the piezoelectric pump 10. the shape of a main flat plate 71C is the same as that of the main flat plate 71, and the shape of a side wall 723C is a shape obtained by changing the shape of the side wall 723 according to the shape of a main plate on the side near the piezoelectric pump 10. In addition, side walls not illustrated also have shapes obtained by changing the shapes of the side wall 721 and the side wall 722 described above according to the shape of the main plate on the side near the piezoelectric pump 10.The main plate on the side near the piezoelectric pump 10 includes a first flat plate part 731C, a second flat plate part 732C, and a third flat plate part 733C. The first flat plate part 731C contacts the outer main surface 40 opof the first housing member 40. the second flat plate part 732C contacts an outer surface 50 sofof the pump housing. The third flat plate part 733C is connected to an end portion of the second flat plate part 732C that is located on the opposite side from the end portion connected to the first flat plate part 731C. The third flat plate part 733C is parallel to and faces the main flat plate 71C.With this configuration, an inner space 700C of the outer housing 70C includes a first space 7001 and a second space 7002. The space consisting of the first space 7001 and the second space 7002 corresponds to a "flow path" of the present invention.The first space 7001 extends along the outer main surface 40 opof the first housing member 40 and the second space 7002 extends along the outer surface 50 sofof the pump housing. With this configuration, heat is dissipated from the piezoelectric pump 10 via the outer main surface 40 opof the first housing member 40 and the outer surface 50 sof the pump housing. Therefore, the pump device 1C can dissipate heat from the piezoelectric pump 10 similarly to the pump device 1.FIG. 9(A) is a graph illustrating changes with time at a discharge temperature for configurations of the present application and a comparative example. In FIG. 9(A), the horizontal axis represents the elapsed time from the start of driving the piezoelectric pump 10, the vertical axis represents the discharge temperature of the piezoelectric pump 10, i.e., the temperature of the outlet 520 of the piezoelectric pump 10. The comparative example illustrates a configuration that does not have a heat dissipation structure like that of the invention of the present application. FIG. 9(B) is a graph illustrating the relationship between the elapsed time and the intake pressure.As illustrated in FIG. 9(A), the configuration of the pump device 1C decreases the rate of increase in the discharge temperature and decreases the temperature that is achieved, as compared with the comparative example. As illustrated in FIG. 9(B), a prescribed suction pressure can be maintained together with the configuration of the pump device 1C for a longer time as compared with the comparative example.Further, by adopting the configuration of the pump device 1C, the rate of increase in the discharge temperature is decreased, and the temperature that is achieved is decreased, as compared with the pump device 1 according to the first embodiment. As illustrated in FIG. 9(B), a prescribed suction pressure can be maintained together with the configuration of the pump device 1C for a longer time as compared with the pump device 1.In addition, as illustrated in FIG. 8, with this configuration, the height of an outer inlet 701C may be made larger than the height of the first space 7001 that communicates with the outlet ports 730. This makes it possible to prevent the outer inlet 701C from becoming a rate-limiting factor for fluid transport.(Third Embodiment)A pump device according to a third embodiment will be described with reference to the drawings. FIG. 10(A) is a side-plane sectional view illustrating the configuration of the pump device according to the third embodiment. FIG. 10(B) is a side-plane sectional view illustrating an example of the wiring for the pump device according to the third embodiment.As illustrated in FIGS. 10(A) and 10(B), a pump device 1D according to the third embodiment is different from the pump device 1 according to the first embodiment in that the pump device 1D includes a plurality of piezoelectric pumps 10. The remaining configuration of the pump device 1D is the same as that of the pump device 1, and a description of identical parts will be omitted.The pump device 1D includes a plurality of piezoelectric pumps 10 and an outer housing 70D. The outer housing 70D includes a main flat plate 71D and a main flat plate 73D, and includes an inner space 700D. The main flat plate 71D and the main flat plate 73D are shaped to allow the plurality of piezoelectric pumps 10 to be arranged side by side.The plurality of piezoelectric pumps 10 are arranged such that the outer main surfaces 40 opthereof are aligned with each other and contact the main flat plate 73D. The main flat plate 73D has discharge ports 730 for each of the plurality of piezoelectric pumps 10. The plurality of discharge ports 730 respectively communicate with the plurality of inlets 400 of the plurality of piezoelectric pumps 10.Here, the plurality of piezoelectric pumps 10 are arranged so as to be arranged with increasing distance from the outer inlet 701 in a direction parallel to the main surfaces of the main flat plate 73D. Thus, the plurality of piezoelectric pumps 10 are arranged side by side in a direction in which the fluid is transported along the flow path.FIG. 11 is a graph illustrating changes over time at a discharge temperature for configurations of the present application and a comparative example. In FIG. 11, N is the number of piezoelectric pumps 10. In addition, the effect of decreasing the rate of increase of the discharge temperature and the effect of decreasing the temperature achieved can be improved by increasing the number of the piezoelectric pumps 10 that are arranged.In addition, as illustrated in FIG. 10(B), in the pump device 1D, wiring electrodes are provided for the piezoelectric elements 20 of the plurality of piezoelectric pumps 10 in a divided manner. Specifically, the piezoelectric elements 20 are each provided with a piezoelectric element 21, a first electrode 22, and a second electrode 23. The first electrode 22 and the second electrode 23 are arranged with the piezoelectric element 21 interposed therebetween. The piezoelectric element 20 is disposed on the vibration plate 31 such that the second electrode 23 contacts the vibration plate 31.The outer case 70D is provided with a divided electrode 290 on an outer main surface of the main flat plate 73D. The second electrodes 23 are connected to the divided electrode 290 via wiring electrodes 280 formed in the pump housings or the like. With this configuration, the wiring for executing driving in the pump device 1D can be simplified even when a plurality of piezoelectric pumps 10 are provided.(Fourth Embodiment)A pump device according to a fourth embodiment will be described with reference to the drawings. FIG. 12 is a side-plane sectional view illustrating the configuration of the pump device according to the fourth embodiment.As illustrated in FIG. 12, a pump device 1E according to the fourth embodiment is different from the pump device 1D according to the third embodiment in the configuration of an outer housing 70E. The remaining configuration of the pump device 1E is the same as that of the pump device 1D, and a description of identical parts will be omitted.The pump device 1E is formed by applying the shape of the outer housing of the pump device 1C illustrated in FIG. 8 to the configuration of the pump device 1D illustrated in FIG. 10. In other words, the outer housing 70E of the pump device 1E includes a main flat plate 71E, first flat plate parts 731E, second flat plate parts 732E, and third flat plate parts 733E. A side wall 723E has the same configuration as the side wall 723C described above. The plurality of first flat plate parts 731E respectively contact the outer main surfaces 40 opof the plurality of piezoelectric pumps 10. the plurality of second flat plate parts 732E respectively contact the outer surfaces 50 sofof the pump housings of the plurality of piezoelectric pumps 10. the plurality of third flat plate parts 733E are respectively connected to the plurality of second flat plate parts 732E. With this configuration, the outer housing 70E has an inner space 700E. The inner space 700E includes a first space 7001 and a plurality of second spaces 7002. The first space 7001 is a space parallel to the outer main surfaces 40 opof the first case members 40 of the plurality of piezoelectric pumps 10. The second spaces 7002 are spaces parallel to the pump housing outer surfaces 50 sof of the plurality of piezoelectric pumps 10. The inner space 700E communicates with the space outside the outer housing 70E via an outer inlet 701E.With this configuration, the pump device 1E also realizes the same heat dissipation effect as the pump device 1D. In addition, since heat is dissipated from the side walls of the plurality of piezoelectric pumps 10, a greater heat dissipation effect is obtained.(Fifth Embodiment)Pump devices according to a fifth embodiment will be described with reference to the drawings. FIGS. 13(A) and 13(B) are sectional top views illustrating the configurations of outer housings of the pump devices according to the fifth embodiment. The pump devices according to the fifth embodiment are different from the pump devices according to the other embodiments in the structure of the outer housing. The remaining configurations of the pump devices according to the fifth embodiment are the same as those of the other embodiments, and a description of identical parts will be omitted.An outer casing 70F of the pump device illustrated in FIG. 13(A) includes a side wall 721, a side wall 722, a side wall 723, a side wall 724, and a partition 725. The side wall 721, the side wall 722, the side wall 723, the side wall 724 and the partition 725 are connected to the main flat plate 71 and are formed to extend in a direction perpendicular to the main surfaces of the main flat plate 71. Although not illustrated, the side wall 721, the side wall 722, the side wall 723, the side wall 724, and the partition 725 are connected to the main flat plate 73 which faces the main flat plate 71.The side wall 721, the side wall 722, the side wall 723 and the side wall 724 are respectively formed so as to extend along the sides forming the outer periphery of the main flat plate 71. The side wall 721 and the side wall 722 are opposed to each other, and the side wall 723 and the side wall 724 are opposed to each other. The side wall 723 is connected to the side wall 721 and the side wall 722. The side wall 724 is connected to the side wall 721 and is not connected to the side wall 722, and a gap is provided between the side wall 724 and the side wall 722. This gap serves as an outer inlet 701F.The partition 725 is connected to an end portion of the side wall 724 on the side near the side wall 722, and separates an inner space 700F into a winding and meandering shaped space. Thus, the fluid flow path has a shape formed by a cylindrical flow path having a winding shape and a cylindrical flow path having a meandering shape connected to each other. The inlet of this flow path is the outer inlet 701F, and a plurality of outlet ports 730 are disposed at the center of the flow path.With this configuration, in the outer housing 70F, the flow rate of the fluid flowing along the flow path can be increased. Thus, the heat dissipation effect for the piezoelectric pump 10 is improved. Further, the side wall 721, the side wall 722, the side wall 723, the side wall 724, and the partition wall 725 are formed of a material having high thermal conductivity such as a metal. Thus, the side wall 721, the side wall 722, the side wall 723, the side wall 724 and the partition wall 725 function as a heat sink. Therefore, the heat dissipation effect for the piezoelectric pump 10 is further improved. Specifically, the partition 725 is longitudinally disposed along the flow path and therefore acts more effectively than a heat sink. Therefore, the heat dissipation effect for the piezoelectric pump 10 is further improved.FIG. 14 is a graph illustrating changes over time at a discharge temperature for configurations of the present application and a comparative example. In FIG. 14, the horizontal axis represents the elapsed time from the start of driving the piezoelectric pump 10, the vertical axis represents the discharge temperature of the piezoelectric pump 10, i.e., the temperature of the outlet 520 of the piezoelectric pump 10. The comparative example illustrates a configuration that does not have a heat dissipation structure like that of the invention of the present application. In addition, the features of the configuration of the first embodiment are also illustrated for comparison of superiority of the heat sink.As illustrated in FIG. 14, the rate of increase of the discharge temperature and the temperature reaching the discharge temperature are decreased by adopting the configuration of the fifth embodiment. In other words, the heat dissipation effect is improved compared with the comparative configuration and a configuration that does not include a heat sink.In FIG. 13(A), the partition 725 has a winding shape and a spiral shape. However, the shape of the partition 725 is not limited to these shapes, and may be a winding shape, a spiral shape, or any other shape that allows a plurality of discharge ports 730 to be disposed along the center of the flow path, and may form a cylindrical shape.An outer housing 70G of a pump device illustrated in FIG. 13(B) includes a side wall 721, a side wall 722, a side wall 7231, a side wall 7232, a side wall 7241, a partition wall 725G1, and a partition wall 725G2. The side wall 721, the side wall 722, the side wall 7231, the side wall 7232, the side wall 7241, the partition wall 725G1, and the partition wall 725G2 are connected to the main flat plate 71 and are formed to extend in a direction perpendicular to the main surfaces of the main flat plate 71. Although not illustrated, the side wall 721, the side wall 722, the side wall 7231, the side wall 7232, the side wall 7241, the partition wall 725G1, and the partition wall 725G2 are connected to the main flat plate 73 which is opposed to the main flat plate 71.The side wall 721, the side wall 722, the side wall 7231, the side wall 7232, and the side wall 7241 are each formed to extend along the sides forming the outer periphery of the main flat plate 71. The side wall 721 and the side wall 722 are opposed to each other. The side wall 7231 and the side wall 7232 are located on the same side of the main flat plate 71. the side wall 7241 is located on the side opposite to the side where the side wall 7231 and the side wall 7232 are located.The partition wall 725G 1 and the partition wall 725G 2 are disposed between the side wall 721 and the side wall 722 so as to be parallel to the side wall 721 and the side wall 722. The partition 725G 1 is disposed to be closer to the side wall 721 than the partition 725G 2.The side wall 721 is connected to the side wall 7231, and the side wall 7231 is connected to the partition wall 725G1. The partition 725G 1 is connected to the side wall 7241, and the side wall 7241 is connected to the partition 725G 2. The partition 725G 2 is connected to the side wall 7232, and the side wall 7232 is connected to the side wall 722.With this configuration, an inner space 700G 1 enclosed in a side surface direction is formed by the side wall 721, the side wall 7231, and the partition wall 725G 1. The inner space 700G 1 communicates with the outside through an outer inlet 701G 1 formed by a gap between the side wall 721 and the side wall 7241. An outlet port 7301 communicates with the internal space 700G1.In addition, an inner space 700G 2 enclosed in a side surface direction is formed by the partition wall 725G 1, the side wall 7241, and the partition wall 725G 2. The inner space 700G 2 communicates with the outside through an outer inlet 701G 2 formed by a gap between the side wall 7231 and the side wall 7232. An outlet port 7302 communicates with the internal space 700G2.In addition, an inner space 700G 3 enclosed in a side surface direction is formed by the partition wall 725G 2, the side wall 7232, and the side wall 722. The inner space 700G 3 communicates with the outside through an outer inlet 701G 3 formed by a gap between the side wall 7241 and the side wall 722. An outlet port 7303 communicates with the internal space 700G3.By adopting this configuration, flow paths can be individually formed for the outlet opening 7301, the outlet opening 7302, and the outlet opening 7303. In addition, in this configuration, therefore, the side wall 721, the side wall 722, the side wall 7231, the side wall 7241, the partition wall 725G 1, and the partition wall 725G 2 further improve the heat dissipation effect for the piezoelectric pump 10.The configuration of the partition walls is not limited to this configuration, and it is sufficient to provide at least one partition wall having high thermal conductivity.In addition, the configurations of the above-described embodiments can be combined as appropriate, and operational effects of these combinations can be obtained.List of reference characters1, 1A 1, 1A 2, 1A 3, 1B, 1C, 1D, 1E pump device 10 piezoelectric pump 20 piezoelectric element 21 piezoelectric body 22 first electrode 23 second electrode 31 vibration plate 32 bottom part 33 support part 40 first housing member 40 opeternal main surface 50 second housing member 50 sfeternal surface 51 main plate 52 side wall 60 third housing member 70, 70A 1, 70A 2, 70A 3, 70B, 70C, 70D, 70E, 70F, 70G housing exterior 71, 71C, 71D, 71E, 73, 73D flat main plate 280 wiring electrode 290 divided electrode 300 flat plate member 400 inlet 500 internal space 501 first space 502 second space 510 nozzle 520 outlet 700, 700C, 700D, 700E, 700F, 700G 1, 700G 2, 700G 3 inner space 701, 701B, 701C, 701E, 701F, 701G 1, 701G 2, 701G 3, 702 outer inlet 710 main flat plate 721, 722, 723, 723C, 723E, 724, 7231, 7232, 7241 side wall 725, 725G 1, 725G 2 partition wall 730 outlet opening 731C, 731E first flat plate part 732C, 732E second flat plate part 733C, 733E third flat plate part 790 cylindrical member 7001 first space 7002 second space 7301, 7302, 7303 outlet opening

Claims

A pump device (1) comprising: a piezoelectric pump (10) including a pump housing having an inlet (400) and an outlet (520); a vibration plate (31) disposed inside the pump housing and partitioning a space (500) inside the pump housing into a first space (501) on a side near the inlet (400) and a second space (502) on a side near the outlet (520); and a piezoelectric element (20) disposed on the vibration plate (31); and an outer housing (70) forming a flow path allowing communication between an outer inlet (701) communicating with the exterior and the inlet (400), characterized in that a first main surface of the outer housing faces an outer main surface (40op) of the pump housing in which the inlet (400) is formed, and the flow path is at least between the outer main surface (40op) of the pump housing and the first main surface of the outer housing (70), the flow path being provided between an outer surface different from the outer main surface (40op) of the pump housing in which the inlet (400) is formed and a surface different from the opposite first main surface of the outer housing.The pump device (1) according to claim 1, wherein the outer main surface (40op) or a surface contacting the outer main surface (40op) is used as a wall surface forming the flow path.The pump device (1) according to claim 1 or 2, wherein the flow path is formed only of a part opposing the outer main surface (40op).The pump device (1) according to claim 1, wherein the outer surface different from the outer main surface (40op) in which the inlet (400) is formed is an outer surface of the pump housing.The pump device (1) according to any one of claims 1 to 4, wherein a length of the outer inlet (701) in a direction perpendicular to the outer main surface (40op) is greater than or equal to a length of the flow path in a direction perpendicular to the outer main surface (40op).The pump device (1) according to any one of claims 1 to 5, wherein a plurality of the piezoelectric pumps (10) are arranged, and the plurality of piezoelectric pumps (10) are arranged side by side such that the outer main surfaces (40op) thereof are flush with the outer housing.The pump device (1) according to any one of claims 1 to 6, wherein a wall of the pump housing in which the inlet (400) is formed is formed of metal.The pump device (1) according to any one of claims 1 to 7, wherein the outer housing has, in an inner space (500) of the outer housing, a partition wall (725) defining a shape of the flow path.The pump device (1) according to any one of claims 1 to 8, wherein the outer housing has a plurality of the outer inlets (701).The pump device (1) according to any one of claims 1 to 9, wherein a wall of the pump housing having the outer main surface in which the inlet (400) is formed forms a part of a wall forming the flow path, and the outer main surface is exposed to the flow path.

Images